1. Field of the Invention
This invention relates to the field of instrument circuits for the measurement of sinusoidal current and, more particularly, to circuits having high accuracy and high stability for signals over a wide bandwidth. The invention, Current Measuring Circuit, conserves space and lowers cost by reducing the size of the associated current sense transformer.
2. Description of the Prior Art
Presently known current scaling circuits typically employ a current sense transformer having a secondary winding that is terminated by a scaling resistor. Conventional prior art circuits develop a small voltage across the terminating resistor. The maximum voltage to be developed across the terminating resistor and the frequency of the current to be measured, as well as the number of turns on the secondary, and the peak design flux density permitted by the core material, combine to control the required cross-sectional area of the core. Increasing the frequency of the current to be measured, or decreasing the required voltage to be supported on the terminating resistor reduces the required cross-sectional area of the core to be used in the transistor. The required voltage to be supported by the secondary was typically reduced by reducing the value of the terminating resistor to a limit that could be conveniently handled by subsequent amplification. Increasing the gain of subsequent amplification stages increased the sensitivity of prior art circuits to noise.